Metal coating process and oil finishing composition therefor



Patented Nov. 6, 1951 T OFFICE METAL COATING PROCESS AND OIL FINISH- ING COMPOSITION THEREFOR George W. Waters, Wood River, 11., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No- Drawing. Application April 12, 1947, Serial No. 741,001

22 Claims. 1

invention relates to metal coating or alloying of'metals. More particularly this invention pertains to oil compositions used in tinning, terne coating, lead coating and the like in order to facilitate and aid in coating or alloying a base metal with a uniform and tenacious metal coatmg.

This process for example, the tinn'ing process comprises-essentially coating base metals by dipand the like said metals into abath-of molten tin thereby coating the base metal with a thin film'of metallic tin. The tinning process is carried out at elevated temperatures and when skillfully done with the aid of good fiuxing agents and proper tinning oils actually forms an alloy of" and the metal being treated which is generally'iron; steel and other ferrous metals. "To-insure strong adherence of the tin to the metal surfacebeingcoated, the metal must be absolutely cleanand free of any grease, dirt, oxide filinand rust. Thisis necessary to insure intimate contact of the metal with the molten tin; terne composition and the like. Metals which are tobe coatedwith tin and the like are thereforecarefully prepared by being properly mechemically" and chemically treated; pickled and kept in slightly acidic solution in order to prevent oxidation of the metal surface prior to enterthe' tinning bath or the like.

" Briefly stated, torexample, one method of tin coating of base metals comprises dipping or passing a properly cleaned metal into' a bath of molten tin, on to an oil bath and then through cleaners to remove excess oil and polish the tinned metal" surface. The general procedure is to pass a mildly pickled metal plate from a slightly acidified storage tank into a tin pot usually divided into a series of compartments; compartment contains a series of rollers through Each which the metal can pass duringits' various: stages oi" tin coating. The molten tin occupies the lower or bottom part of the tin pot. On the deed end of the pot floats a layer of flux and on the exit end floats a much' deeperlayer of oil.

The flux serves to give final preparation of the .metal' surface before being immersed into the molten tin. It consists generally of zinc chlcride'or mixtures of zinc" chloride and sodium chloride'or ferric chloride ora'mmonium chloride and the. like. The function or purpose of the flux is to cleanthoroughly the metal surface, remove moisture, absorb any oxide film, pickling scumand control more or less the wetabili'ty ly to the metal surface. treated. r

From the" fluxlng bath the metal proceeds on through a series of rollers through a molten tin bath kept at a temperature of between about 525 F; to above about. 800 F. and preferably between about 530 and about 560, depending upon the" operating conditions. The tinned metal then proceeds through an oil bath while passing' through rollers where excess tin is removed, better distribution of the tin coating is secured and oxidation of the tin is inhibited. The tinned metal having a thin film of oil on it proceeds on out of the oil bath and receives a cleaning treatment where excess oil is removed. Any remaining oil left on the metal aids in polishing the'metal to a desired surface finish.

Articles of odd shape can be tin coated by mechanical or hand dipping into a flux coating tin pot and then redipped' into an oil coated tin pot which on withdrawal come in contact with the'oil' and receives its beneficial treatment. If desired, the metal can then be immersed into a hot oil bath for final oil treatment in order to control more closely the thickness of the tin coating, and also such oil treatment acts to some degree as a quenching medium.

Timing oils play' a vital role in the tin'p'lating art for they serve to secure better distribution of tinon the base metal being coated, aid in removal of excess tin and protect the tin from oxidation" or discoloration while being cooled. To accomplsh these and other features a good tinnihg oil must be capable of absorbing" oxides so as to keep the metal surface clean; it must have a suitable interfacial' tension with molten' tin and with the atmosphere and it must be stable and not tend to deteriorate or polymerize even afterlong periods of use under extremely high temperatures. E'fficient' tinn'ing oils" should in addition form a uniform film on the coated metal surface while in the tin but on emerging from thepot drain oli easily and quickly. Oils which do not drain oii easilymust be continuously replaced which is quite an expense. Such oils may also tend to form globules or isolated patches on the tinnedsurface which produce depressions on the tin coating, resulting in localities which are very thin and which form grease marks on the tinned surface. 7

One main criterion of a goodqtinning oil as stated above is its ability to drain off rapidly from the tinned article as it emerges from the hot oil bath. From this aspect straight mineral oils and. even palm oil after relatively short periods of use are not satisfactory. This desirable phenomenonof rapid. draining seems to be associatedwith. the presence ofcertain polar bodies in the oil. An oil containing a plurality of these polar bodies drains off rapidly and leaves the tinned surfaces clean and bright. It is assumed that such oil films tend to form one or more aggregates which move continuously over the surface in an apparently random fashion. As the activity of the aggregates becomes reduced owing to reduction of these polar bodies, the draining of the oil is reduced and eventually a continuous film state is reached where the draining properties of oils are considerably retarded and the oil is no longer suitable for use. It is postulated that the efficiency of such oils is due to the formation of a monomolecular absorbed layer over the surface of the tin.

Generally oils used in tinplating are subjected to elevated temperatures of at least 460 F. and higher for lon intervals. It is therefore essential that such oils be chemically stable at such temperature, Without undue volatilization, decomposition or polymerization.

, Palm oil is known to be an efficient tinning oil. However, it has several serious drawbacks in that it is costly, difiicult to obtain and above all polymerizes readily at temperatures about 470 F. resulting in sludging and high oil losses. Also other beneficial tinplate properties of palm oil are destroyed at temperatures above 470 F. At

this elevated temperature palm oils leave on the tinplate streaks of oil resulting in a dull, lustre less coated surface.

It is an object of this invention to produce an excellent tinning oil having a petroleum hydrocarbon base. Another object of this invention is to produce a new and improved tinning oil which is stable at extremely high temperatures for long periods of time. Another object of this invention is to produce a new and improved tinning oil having the ability to take up oxide, to readily absorb flux residue and to promote the spreadin of tin and other molten metals. Still anotherv object of this invention is to produce a tinning oilwhich does not stain or have bad effects on the coated surf-ace if left on. Furthermore, it is another object of this invention to produce a tinning oil which drains and cleans easily and which is not a fire hazard.

The above and other objects may be attained in accordance with the present invention by ad- 'mixing with a mineral oil base containing a minor amount of a high boiling nitrogen-containing organic compound or mixturesof nitrofgen-containing organic compounds, a suitable amount of hydrogenated animal, vegetable, mar- ,ine oils, distillate and residuum fractions of said oils and mixtures of said oils and/or their fractions.

Among the hydrogenated animal, vegetable and marine oils and their fractional derivatives which can be used for metal coating compositions of this invention are:

[ill

4 B. Semi-drying oils Corn oil, cottonseed oil, kapok oil, rapeseed oil, ravison oil, sesame oil, sunflower oil, teaseed oil, rice bran oil, etc. 0. Drying oils Linseed oil, oiticica oil, perilla oil, soybean oil, tung oil, poppyseed oil, hempseed oil, etc. III. Marine and fish oils Codfish oil, codliver'oil, dogfish oil, dolphin body oil, dolphin fish oil, herring oil, Japfish oil, menhaden oil, porpoise body and jaw oils, salmon oil, sardine and sardine liver oils, seal oil, shark and shark liver oils, sperm whale body and head oils, whale oil, etc.

IV. Hydrogenated residuum fractions obtained from oils listed under Groups I, II, and III.

V; Hydrogenated distillate fractions obtained from oils listed under Groups I, II, and III. 'Hydrogenation of any of the above oils, their in the presence of steam and a suitable catalyst. so that the resultant hydrogenated product is.

acidic. The hydrogenated product should be added to a mineral oil base containing a nitrogen-containing organic. compound in amount sufficient to maintain the acid number of the tinning or metal coating oil composition at not less than 3 and not above about 15, and preferably between about 4to 10. In order to maintain the acid number of the composition at approximately these values, a replenishing agent is added to the oil composition during use. The replen ishing agent comprises a concentrate of mineral oil and hydrogenated fatty oil and/ or fractions of hydrogenated fatty oils such as the hydrogenated distillate or residuum fractions made up in a ratio varying from 1:3 to about 3:1 parts by weight of each ingredient respectively and preferably the replenishing concentrate is made up ofequal parts by weight of mineral oil and the hydrogenated fatty product. The replenishing concentrate is added in amounts sufilcient to adjust the acid number of the base composition to not less than about 3 and not above about 15. The amount of organic nitrogen containing compound used to stabilize the composition against oxidation deterioration and the like varies from between about 0.25 to 2.0% and preferably between about 0.5 to 1.0% by weight.

v Of the hydrogenated fatty oils and their fractions enumerated above, the preferred tin and metal coating additives are the hydrogenated fish and/ or marine oil'distillates and their mixtures. The fish and/or marine 'oil distillate products can be recovered from such oils by any conventional means and then hydrogenated or the oil,

can be hydrogenated first and the product then split and the overhead distillate fraction. removed by distillation, extraction, and the like. For example, a fish oil such as herring oil, menhaden oil and the like, can be hydrogenated and split and subsequently distilled to produce an overhead distillate of hydrogenated fish oil. Another preferred fatty oil fraction is obtained by splitting the above hydrogenated fish oil distillate fraction, removing the overhead distillate and utilizing the hydrogenated residuum fraction as the tinning oil additive. The residue product is generally referred to in the trade as fatty acid 5 The pitch can be further split, subjected to distillation, the overhead distillation fraction recovered,-hydrogenated and combined with the first overhead distillate product and used as ad-' .diti-ve products in this invention. Another method of producing the desired distillate fractions is to split the oil first, remove the distillate fraction and then hydrogenate it preferably in the presence of a suitable catalyst and at elevated temperatures.

The overhead distillate products such as described above or those obtained from other fatty oils are not to be confused with the residue prod nets generally referred to as residuum prod ucts or pitches. The two fractions are entirely separate and distinct chemically from each other and also from the base oil from which they are derived. As will be hereinafter shown superior results are obtained when hydrogenated fish oil distillates are utilized as tin and metal coating 011 additives. However, hydrogenated residuum products derived from fish oils or other hydrogenated fatty oil products can be used for tinplating oil compositions when in combination with an organic nitrogen-containing stabilizing agent.

Analysis of a hydrogenated marine oil, and its residuum and distillate fractions is given below:

' Hydro Hydrov oen ated genated Hope-hes fiffi' g Marine Oil Marine Oil r Distillate Residuum Specific Gravity, 60 F. 0.926 0.950 0.898 Melting Point, F .1 101 145 134 Acid number. 1. 188 149 Iodine number 58.34 3.6 23

Anti-oxidants which are particularly applicable for use with compositions of this invention none, l-amino-1,2-naphthohydroquinone, thiodiphenylamine, monobenzyl para amino phenyl, ZA-diamino toluene, 2,4-diamino diphenyl amine, para amino ozobenzene, octadecyl benzyl amine,

.beta phenylamine-alpha-naphthylamine, phenyla naphthylamine, phenyl 3 naphthylamine.

.diamino diphenyl methane, p,p'-diamino diphenyl methane, 4,4-diamino diphenyl methane,

tetraethyl diamino diphenyl methane, diisoamyl dlamino diphenyl methane, bis-(pB-naphthyl amino methyl) -p-tertamyl phenol;

3,3,5-tricyclohexylamine, dicyclohexylamine; N-phenyl morpholine, 'N-(parahydroxyphenyl) morpholine;

octadecyl 3-methyl-2-pentylamine, N-octadecyl- 2-ethylhexylamine, hexadecylamine, octadecylamine, octadecenylamine, octadecadienyl amine, parafiine waxamine, cocoamine prepared from 'cocoanut oil acids, N,N'-dimethyl triglycol diamine;-. disalicylal ethylene diamine; N-salicylal- .li'et iaael-ei y e el. em ei --.m hi n 2341 .N;N'-.dibutyl paraphenylene diamine, tetra methyl A and meta toluylene diamine, mixture of dipara methoxy diphenyl amine, diphenyl para-phenylene diamine and phenyl beta naphthyl amine, mixtures of phenyl-fl-naphthylamine and meta toluylene diamine, mixture of diphenyl para phenylene diamine and para phenylene diamine,

mixture of stearic acid, meta toluylene diamine and phenyl-..a-.naphthylamine, mixture of ditolylamine and petroleum .wax. and the like. The amines which are particularly preferred are; phenyl-a-naphthylamine, phenyl s naphthylamine, beta phenyl-amine a naphthylamine, tetra methyl diamino diphenyl methane, meta toluylene diamine, their mixtures and amines having a boiling point of or above that of phenyl-anaphthylamine, although this is not a critical limitation but a desirable one.

The addition of nitrogen-containing organic compounds to oil compositions of this invention in addition to inhibiting the oxidation tendencies of the composition greatly improves its tinning properties and stability. In addition it decreases the loss of acid from theoil, reduces the viscosity and improvesthe draining of'the-oil from the tin plate.

The mineral oil base used can be any suitable refined petroleum hydrocarbon stock having high flash and fire points and which are substantially stable at tinning temperatures of between about 460-490 F. Suitable petroleum hydrocarbon base stocks which can be used are solvent extracted Mid-Continent Bright stock, acid treated Mid-Continent Bright stock; acid treated naphthenic neutral stock and blends of these .011 stocks. Preferably, however, solvent extracted Mid-Continent Bright stock having a Saybolt Universal viscosity at 210 F. of -470 is used as the oil base stock because of the superior tinplating -re-- sults obtained when using this type of oil.

To more fully and clearly illustrate this invention a series of comparative tinning tests were conducted in which the tinning performance as to flux removal, drainage characteristic, ease of cleaning and spreadability characteristics of the following oil compositions were compared:

Code No.

1. Mineral oil (solvent extracted Mid-Continent oil, 150-170 SUS at 212 F.).

2. Palm oil.

3. 20-50% by wt. of palm oil in mineral oil base.

4 Mixture of hydrogenated cottonseed oil in mineral oil base having an acid number of less than 3.

5. Mixture of hydrogenated fish oil residuum or stearine pitches in mineral oil having an acid number of 3 to 15.

6. Mixture of hydrogenated fish oil residuum or stearine pitches in mineral oil having an acid number of 3 to 15 and containing about 0.5% by wt. of phenyl-a-naphthylamine.

7. Mixture of hydrogenated fish oil distillate in mineral oil having an acid number of 3 to 8. Mixture of hydrogenated fish oil distillates in mineral oil having an acid number of 3 .to 15 and containing about 0.5% by wt. of

' phenyl-e-naphthylamine.= 9. Mixture of hydrogenated fish oil distillates in mineral oil having an acid number of 3 B. Another test was conducted in which the tinningtechnic was slightly modified. Two' tinning pots were used as before, and the temperature of the first tin pot was kept at 535 F. and

tetra meth l diamino di hen l methane; p suflicient to form, a ring covering the bathedges was used to keep the surface clean. Immediately t H01 ed (3 i pot, it was transferred to an oil pot kept at a were i 9 1 d temperature of 460-4'75F. To simulate theoil- 2 plus 1 10 gi a i lgg g i tin interface encountered in tinplate manua empera ures 8 ween a 011 an .8, 011 560 F d r f 1 m t 550 F The finnm facture asmall amount of tin was poured into an D e e a y a g the bottom of the 011 pot. Tests were conducted pot Su Was ver Wlllh Sheets were 15 for a 72 hour period with the same compositions tinned S0 that Very little, if flux adhered to as indicated in TableI and the results weresub the sheets upon withdrawal. Immediat ly after stantially the same as indicated in Table I. withdrawal, the sheets were transferred to a fin- C. Still another test was conducted in a small ishing pot containing tin at about 53O-54 5 F. tinning machine similar to that describedinoolq. and a superimposed layerof oil at about 460-490? u mns l andz... The tin was el P ln'the R and pr f r bly at The re1ative1y.high 011 pot and. the flux and 011 tested put in the feed temperaturewas necessary to maintain the den f or exlt compartments of the i sired oil temperature. Here the sheets were imgfis g g igg g f r s 1 gg i mersed in the tin and then drained in, the oil s g igg ch oil were g gg i ig gz layer. The metal sheets were immersed in the a u 1 g tir and then drained the on layer .Metal hour interval and the tmnmg performance .of the t t d e n rm t eat oils as to flux remov'al, draining characteristics, 5 rips tes e 1N6!- iIVG 1a 1 lith i t 0 ease of cleaning and spreading characteristics ment regu erva s and es was were noted. The results again were similar to s d for of 72 .hoursproperifles those disclosed in Table I, showing the superiority as indicated 1n Table I were graded in descending of ineral oil-hydrogenated fish oil distillates order, (1) being the best, (2) next best, etc. The Over 0115 tested as a tinnjng n results of the test :were as follows: 'D.- Tests were conducted according to .pro-

TABLE 1 Code No; Flux Removal Draining Charac- Ease of Cleaning Spreading Char- Total Remarks teristlcs acteristics l 10. Poor flux're- 10. streaked b d- 10. F 1ux spots, 10. stained,'stri 40 Mineral alone wasround totallyunsuit moval. ly. stained, sticky p e d, )1 ea vy able. At the end of 24 hours sludge and diflicult'to tinned. formations were high and losses clean. heavy dso that test had to bedis- Y coun e 2 3. Showed good 5. Good draining 4. Easy but flux 3, Good at early 15 Although the timing characteristic of flux removal for characteristics spots noted. stage but spanpalm oil were good for 24h0urs; oil 72 holllrtestfor early P Of gled about 24' losses were heavy at the end of the testbutstreaked hours. 72 hour test. after 48 hours. r I 3. (30 Z, 6. 8. Poor through- 8. Easy toremove [Stained 29 After 24 hours the tin plate was stained Palm oil out test period. but flux spots and Spangled. Stripping was noted inmincral noted. and draining was poor throughout oil): test. At the end of 24 hours test was 1 V discontinued. 4 6. -10. Streaked bad- 8. Stainedauddif- '10; Stained, um 34 After a short period the oil was found 1y. ficult to clean. ning not very to be unsatisfactory and test was uniform. discontinued. 5 3. 8. Poor throug 8. Good draining 4. Fair 21' Fluxremovaland spreadingwere good. out test period. early perlod of Draining and cleaning-were poor and test but became became increasingly worse. I worse later. a 6 3. Good flux re- 5. Good draining 3. Good 3. Good at begin- 14 The addition of the amine antioxidant move] for 72 at first but bening of test but resulted inaproduct equivalent to or hours. came wor e as left stains. superior to palm oil. n

test continued. 7 1. Good 3. Good for 48 3. Same 2. Good 10 Flux removal and spreading were good. hours, but at I 7 Exhibited a pronounced stabilizing end of test peeffect on the composition and gave IlOd showed good tinning performance at theond signs of poor. 5 of 48 hours and fair tinning per formdrainmg. ance at the end of 72 hours. Oil losses were only la 01' that of palm oil after 72 hrs. 8 1. Very good 2. Good for entire 2. Good 2. Good 7 Fluxremovalandspreadingweregood. 72 hour test. Exhibited a pronounced stabilizing effect on the composition and gave good tinning performance for entire 72 hour test period. Oil losses'were only V3 of that of palm oil aiter'72 hours and required 8.8% by wt. less replenishing agent so as to maintain the acid number of the composition between 3 and 15 than was required for composition of Code N o. 5. 9 1. Very good 2 2 2 7 'Fluxrcmovaland spreading weregood. Exhibited a pronounced stabilizing effect on the composition and gave good tinning performance for entire 72 hour test period. Oil losses were only $6 of that of palm oil after 72 hours and required 8.8% by wt. less replenishing agent so as to maintain the acid number of the composition between 3 and 15 than was required for composition of Code No.

7 Mineral oil-hydrogenated fish oil 9 edure outlined under A and B in order to determine the criticalityof maintaining the acid number of mineral oihhydrogenated fish oil distillates between about 3 to 15.

To further show the marked effect on oxidation stability nitrogen-containing organic compounds have on tinning oil compositions of this invention the Dornte oxidation test as fully described in the TABLE II Spread- Draming Flux Re- Ease of m I Oharacc Total Remai ks moval Oleaniii Charactensucs g tei'istics 1 Mineral oil-hydrogenated fish oil distillates having an 8 9 7 6 30 Drained very poorly and unacid number less than 3. St ble. 2 Mineral oil-hydrogenated fish oil distillates having an 3 6 7 4 20 Cause etching of metal surface acid number greater than 15. and difiicult to clean. 3 Mineral oil-hydrogenated fish oil distillates having an 2 3 3 2 10 Good. spreading characteristics acid number between about 4-40. and stable. 4 Mixture oi mineral oil and hydrogenated fish oil distill 2 2 2 7 Flux and draining properties imlates having an acid number of 15 and containing proved and no sludge was 0.5% wt. phenyl'mnaphthylamine. I noted after a 72 hr. test run. 5 Mixture of mineral oil and hydrogenated fish oil distill 2 2 2 7 Flux and draining properties imlates having an acid number of 15 and containing proved and no sludge was t ).5% wt. tetra methyl diamino dipl cnylinethane. noted after a 72 hour test run. 6 Mineral oil-hydrogenated cott riseed oil having an acid 6 l0 8 10 34 Product unsatisfactory as a tinnnmber of less than 3 (0.62). ning composition.

AS has been repeatedly pointed outthe acid number of a suitable tinning oil composition must be kept at not less than 3 and not above about 15. Due to the elevated temperatures under which tinning compositions and the like are used the acid number varies and in order to readjust it within the desired acid range a replenishing agent isv used. The replenishing agent consists essentially of a concentrated mineral oil and a desired hydrogenated fatty oil or any of its fractions. but preferably the overhead distillate traction made up in the ratio varying from 1:3 to around about 3:1 parts by weight of each ingredient respectively. Preferably the above ingredients should be mixed in approximately equal parts. and is added to the base composition in amounts. sufiicient to readjust the acid number between about 3 to 15.

A quick and conclusive test was developed to study the draining characteristics of tinning oils. A heavily tinned plate was immersed for seconds into an oil kept at a temperature of approximately 480 F. Heavily tinned plates were repeatedly dipped in the various oils during a 24 hour interval and the characteristics of the oil film remaining on the plate were preserved by printing of! on a hard filter paper and observations made.

TABLE III Composition 1 Mineral oil Drained poorly through test period. Filter paper covered with a heavy oil film.

2 SOZ JYHWL of Palm oil in min- Drained poorly, paper co bet between 3 and 15.

6 Mineral oil-hydrogenated fish oil 7 residuum product having an acid number between 3 and 15.

tcristics. Drained poorly, paper covered with an oil film.

Results similar to palm oil.

residuum product having an acid number between 3 and 15 and containing 0.5% by Wt. of

phenyl-a-naphthylamine.

8 Mineral oil-hydrogenated fish oil distillates having an acid number oetween 3 and 15.8.1111 contalnng 0.5% by wt. of phenylanaphthylamine.

Composition of 6 but the antioxidant used 7 here is tetra methyl diammo diphenyl methane. 7

Mineral oil-hydrogenated cottons'eed oil having an acid number of less than 3.

Superior to palm oil in drain ing characteristics.

Drained very poorly during test period.

Industrial Engineering Chemistry of August 1942, volume 34, page 927, was conducted and compared with other tinning oil compositions.

TABLE IV Domte. Oxidation Test. minutes volume oxygen absorbed, 1800 cc./ cm. oil 313 F. copper present Per Cent lhenyl-a-naplithylamine added- Mineral Oil of hydrogenated fish oil distillates in mineral oil having an acid number of 15 (8.0% by wt. of the distillate).

None... 0.5% wt. 290 385.

Composition 1 and Data Remarks CodeNo. 7 Code No.8

Amount of replenishing agent required during test period in order to maintain the acid number at 15.

8.8% by wt. less than that used in Code No. 7.

1 7 and 8 are the same composition as referred to in Table I.

Viscosity changes in the compositions after'the following number of test hours (S. U. S. at 210 F):

Viscosity Viscosity Hours changes for changes for Code No.7 CodeNo.8

composition can be made in order to obtain an improved tinplate'with the use of composition of this invention. Thus, minor amounts of high molecular fatty acids such as oleic, stearic and the like can be added to compositions of this in-@ vention to improve the lustre of the tinplate, and spreadability of the tinning composition. Also non-hydrogenated animal and vegetable oils such as cocoanut oil, castor oil, cottonseed oil, peanut oil and the like as well as synthetic lubricants produced by polymerization of olefins can be admixed with composition of this invention.

Compositions of this invention are not restricted to use in tinplating only but are equally applicable for terne coating, lead coating and the like. Neither are these compositions restricted to use where metal plating is done only by dipping and the like. Compositions of this invention can be used to improve the metal coating surface and deposition of metals on metal base by electrolytic methods as well as any other known metal plating method. The appearance of surfaces having tin deposited thereon by electrolytic means is greatly improved by dipping such metal treated surfaces into a hot bath comprising an oil composition of this invention.

In addition to being equal to and in most properties superior to palm oil, compositions of this invention have a particular advantage over palm oil in that they reduce to a minimum the danger of fire hazard.

It is to be understood that while the features of the invention have been described and illuswherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath consisting essentially of a zinc chlorideammonium chloride solution, followed by passing the metal into a molten tin bath maintained at a temperature or between about 530 and about 560 F., and passing said tin-treated metal through an oil composition maintained at a temperature of between about 460 and about 500 F., the improvement residing in using as said oil composition a mixture consisting essentially of mineral oil and partially hydrogenated fish oil distillates, said mixture having an acid number of not less than 3 and not more than about 15, and containing a minor amount suflicient to stabilize the composition against deterioration a-naphthylamine. v r

2. In a method of tin coating a metal surface wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath consisting essentially of zinc chlorideammonium chloride solution, followed by passing the metal into a molten tin bath maintained at a temperature of between about 530 and about 560 F. and passin said tin treat-ed metal through an oil composition maintained at a temperature of between about 460 and about 500 F., the improvement residing in using as said oil composition .a mixture consisting essentially of mineral oil and partially hydrogenated fish oil distillates, said mixture having an acid number of .not less than 3 and not more than about 15 and containing a minor amount suflicient to stabilize the composition against deterioration of tetra methyl diamine diphenyl methane.

3. In a method of tin coating a metal surface of phenyl- V 12 wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath consisting essentially of a zinc chlorideammonium chloride solution, followed by passing 0 the metal into a molten tin bath maintained at a temperature of between'about 530 and about,

' containing a minor amount suflicient to stabilize the composition against deterioration of meta toluylene diamine. I

4. In a method of tin coating a metal surface wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath consisting essentially of a zinc chlorideammonium chloride solution, followed by passing the metal into a molten tin bath maintained at 'a temperature of between about 530 and about 560 F.. and finally passing said tin treated metal through an oil composition maintained at a temperature of between about 460 and about 400 F. the improvement residing in using as said oil composition a mixture consisting essentially of mineral oil and partially hydrogenated fish oil distillates, said mixture having an acid number of, not less than 3 and not more than about'l5 and containing a minor amount sufflcient to stabilize the composition against deterioration of a high boiling unsubstituted hydrocarbon amine.

5. In a method of metal coatin a metal surface of a base metal whereinsaid base metal is cleaned and pickled and .wherein said cleaned metal is passed through aflux bath, onthrough a molten metal bath selected from the class consisting of molten tin, molten lead and a. molten metal mixture of lead and tin, and finally passing said metal through an oil composition, maintained at an elevated temperature, the improvement residing in using as said oil composition a blend consistin essentially of mineral oil and partially hydrogenated fish oil and marine oil 'distillates, said blend having an acidnumber of not less than 3 and. not more than about-15, and containing a minor amo'ut sufficient to stabilize the compositionagainst deterioration of a high boilingunsubstituted aryl amine. V

6. In a method of'metal coating ametal surface of a base metal wherein said base metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath, on through a molten bath selected from the class consisting of molten tin, molten lead and a molten metal mixture of lead and tin, and finally passing said .metal throughan oil composition, maintained at an elevated temperature, the improvement resid- -ingin usin as said oil composition a blend consisting essentially of mineral oil and partially hydrogenated fish oil and marine oil distillates, said blend having an acid number of not less than 3 and not. more than about 15, and containing a minor amount suflicient tostabilize-the composition against deterioration of a high boiling'unsubstituted hydrocarbon amine. v'

7. In a method of tin coating a. metal surface wherein a metal is cleaned and pickled and wherein said cleaned metal is passed througha flux bath consisting essentially of a zinc chlorideammonium chloride solution, followed bypassing the metal into amolten tin .bathrmaintained at a temperature of between aboutSeO and about 56o F. and finally passing said tin treated metal. through an oil composition, maintained at a tem perature of between about 460 and about 430 F'..

the improvement residing in using as said oil composition a mixture of mineral oil and partially .hydrogenated fish oil distillates and a minor amount sufficient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine, said oil composition being replenished'at intervals with a concentrate comprising approximately equal parts of a mixture of hydrogenated fish oil distillates and mineral oil, in amounts sufiicient to maintain the acid number of said oil composition between about 3 to 15. ,8. In a method of metal coating metal surfaces wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux metal bath, on through a molten metal ba h selected from the class consisting of molten tin,

molten lead and mixtures of molten lead and tin and finally passing said metal through an oil composition, maintained at an elevated temperature, the improvement residing in using as said oil composition a blend consisting essentially of mineral oil and partially hydrogenated fish oil distillates, containing a minor amount sufficient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine, said composition being replenished at intervals. with a 1':

concentrate comprisin approximately equal parts of a mixture of hydrogenated fish oil d i s tillates and mineral oil, in amounts sufficient to maintain the acid number of said composition between about 3 to 15.

9. In a method of metal coating metal surfaces wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a flux bath, on through a molten bath selected from the class consisting of molten tin, molten lead fractions of said oils, said blend having an acid number of not less than 3 and not more than about 15 and containing a minor amount sufiicient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine.

10. In a method of tin coatin metal surfaces wherein a metal is cleaned and pickled and wherein said cleaned metal is passed through a fiux bath consisting essentially of a zinc chlorideammonium chloride solution, followed by passing the metal into a molten tin bath maintainedat a temperature of between about 530 and about 560 F. and finally passing said tin treated metal through an oil composition, maintained at a temperature of between about 460 and about 490 F'., the improvement residing in using as said oil composition a blend consisting essentially of mineral oil and hydrogenated fatty oil, said blend having an acid number of not less than 3 and not more than about 15, and containing a minor amount sufiicient to stabilize the composition against deterioration of a high boilin unsubstituted aryl amine. I

11. In a process of aiding in forming an adherent tin coating on ferrous surfaces thestep off contacting-said tin coated surface. with a composition consisting essentially of anoil blend of mineral oil and partially hydrogenated fish oil distillates and a minor amount sufficient to stabilize the composition against deterioration of phenyl-a-naphthylamine, said composition having an acid number of between about 3..and 15.

- 12. In a process of aiding in formin an adherent tin coating on ferrous surfaces, the. step of contacting said tin coated surface with a composition consisting essentially of an oil blend of mineral oil and partially hydrogenated fish oil 'distillates and a minor amount sufiicient to meta toluylene diamine, said composition having an acid number of between about 3 and 15.

14. In a process of aiding in forming an adherent tin coating onferroussurfacespthe step of contacting said tin coated surface with a composition consisting essentially of an oil blend of mineral oil and partially hydrogenated fish oil distillates and a minor amount suiiicient to stabilize the composition against deterioration of a high boilin unsubstituted hydrocarbon amine, said composition having an acid number of be-- tween about 3 and 15.

15. In a process of aiding in forming an adherent metal coating on ferrous surfaces, the step of contacting said tin coated surface with a. composition consisting essentially of a mixture of mineral oil and partially hydrogenated fish oil distillates and a minor amount sufficient to stabilize the composition against deterioration of a high boiling unsubstituted hydrocarbon amine, said composition bein replenished during use with a concentrate comprising approximately equal parts of a mixture of hydrogenated fish oil distillates-mineral oil, in amounts sufficient to maintain the acid number of said composition between about 3 to 15.

16. A mineral oil composition suitable for aiding in the formation of an adherent coating on ferrous surfaces with molten metals selected from the class consisting of tin, lead and mixtures of tin and lead, consisting essentially of a blend of mineral oil and partially hydrogenated fish oil distillates and a minor amount sufiicient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine, said composition having an acid number of between about 3 to 15.

17. A mineral oil composition suitable for aiding in the formation of an adherent tin coating on ferrous surfaces, consisting essentially of a blend of mineral oil and hydrogenated fatty oil residuum fractions of said oils and hydrogenated distillate fractions of said oils and aminor amount sufficient to stabilize the composition against deterioration of a high boiling-unsubstituted hydrocarbon amine said composition having an acid number of between about 3 to 15.

19. A mineral oil composition suitable for aiding in the formation of an adherent coating on ferrous surfaces with molten metals selected from the class consisting of tin, lead'and mixtures of tin and lead, consisting of a blend of mineral oil and partially hydrogenated fish oil distillates and a minor amount sufficient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine, said composition having an acid number of between about 3 to 15.

20. A mineral oil composition suitable for aiding in the formation of an adherent coating on ferrous surfaces with molten metals selected from the class consisting of tin, lead and mixtures of tin and lead, consisting of a blend of mineral oil and partially hydrogenated fish oil distillates and from 0.25% to 2% sufficient to stabilize the composition against deterioration of a high boiling unsubstituted aryl amine, said composition having an acid number of between about 3 to 15.

21. A mineral oil composition suitable for aiding in the formation of an adherent coating on ferrous surfaces with molten metals selected from the class consisting of tin, lead and mixtures of tin and lead, a blend consisting essentially of mineral oil and a hydrogenated fatty oil, said blend having an acid number of between 3 and 15 and containing a minor amount sufficient to stabilize the composition against deterioration of a high boiling unsubstituted hydrocarbon amine.

22. A mineral oil composition suitable for coating on ferrous surface with molten tin, a blend consisting essentially of mineral oil and hydrogenated fish oil distillate having an acid number of between 3 and 15 and containin phenyle naphthyl amine in an amount sufiicient to prevent deterioration of said blend.

GEORGE W. WATERS.

REFERENCES CITED The following references are of record inthe file of this patent:

r UNITED STATES PATENTS Number OTHER REFERENCES Oil, Paint andDrug Reporter, October 23, 1939, page 52. v 7

Oil, Paint and Drug Reporter, October 30, 1939, page 30. 7 

9. IN A METHOD OF METAL COATING METAL SURFACES WHEREIN A METAL IS CLEANED AND PICKLED AND WHEREIN SAID CLEANED METAL IS PASSED THROUGH A FLUX BATH, ON THROUGH A MOLTEN BATH SELECTED FROM THE CLASS CONSISTING OF MOLTEN TIN, MOLTEN LEAD AND A MOLTEN METAL MIXTURE OF LEAD AND TIN, AND FINALLY PASSING SAID METAL THROUGH AN OIL COMPOSITION, MAINTAINED AT AN ELEVATED TEMPERATURE, THE IMPROVEMENT RESIDING IN USING AS SAID OIL COMPOSITION A BLEND CONSISTING ESSENTIALLY OF MINERAL OIL AND A HYDROGENATED FATTY OIL SELECTED FROM THE CLASS CONSISTING OF HYDROGENATED ANIMAL, VEGETABLE, MARINE OILS, HYDROGENATED RESIDUUM FRACTIONS OF SAID OILS AND HYDROGENATED DISTILLATE FRACTIONS OF SAID OILS, SAID BLEND HAVING AN ACID NUMBER OF NOT LESS THAN 3 AND NOT MORE THAN ABOUT 15 AND CONTAINING A MINOR AMOUNT SUFFICIENT TO STABILIZE THE COMPOSITION AGAINST DETERIORATION OF A HIGH BOILING UNSUBSTITUTED ARYL AMINE.
 18. A MINERAL OIL COMPOSITION SUITABLE FOR AIDING IN THE FORMATION OF AN ADHERENT TIN COATING ON FERROUS SURFACES, CONSISTING ESSENTIALLY OF A BLEND OF MINERAL OIL AND A HYDROGENATED FATTY OIL SELECTED FROM THE CLASS CONSISTING OF HYDROGENATED ANIMAL, VEGETABLE AND MARINE OILS, HYDROGENATED RESIDUUM FRACTIONS OF SAID OILS AND HYDROGENATED DISTILLATE FRACTIONS OF SAID OILS AND A MINOR AMOUNT SUFFICIENT TO STABILIZE THE COMPOSITION AGAINST DETERIORATION OF A HIGH BOILING UNSUBSTITUTED HYDROCARBON AMINE, SAID COMPOSITION HAVING AN ACID NUMBER OF BETWEEN ABOUT 3 TO
 15. 